There has been great interest in the neuroscience community in decoding the functioning of the brain. Among the various methods used, analysis of the recordings of the electrical activity of neurons has been among the most important tools available. These recordings can be indispensable for understanding and diagnosing neurological disorders like epileptic seizures, in the creation of brain-machine interfaces, and for neuro-prosthetic technologies to aid paralyzed patients. Further, modern neuroscience is attempting to “close the loop” with the brain, by stimulating specific areas using current pulses, and recording neuronal responses to learn and adapt the stimulation patterns. For example, it has been demonstrated in a limited number of patients that stimulating certain regions of the entorhinal cortex of the brain could improve memory function.
Typically, extracellular recordings of neural signals occupy a frequency band from 1 Hz to about 5 kHz, and have relatively small amplitudes, ranging from 1 mVp for Local Field Potentials (LFPs) to 100 μVp for Action Potentials (APs). Due to their small amplitudes, neural signals are often amplified before digitization. Where the peak input-signal amplitudes are on the order of 1 mV, the input-referred noise of an amplifier should be less than 4 μVrms for 8-bit resolution. Thus, low-noise bio-signal amplifiers could be utilized in various signal recording systems including (but not limited to) recording neural signals.